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Question 1
Solution Z contains three different negative ions. To a sample of solution Z a pupil adds
The observations after each addition are recorded in the table below. |
a) | Give the formulas of A and B. Suggest the identity of two of the negative ions.
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The white precipitate B is removed from the solution by filtration. To the filtrate the pupil adds
Some of the observations are recorded in the table below. |
b) | Give the formula of C. Write an ionic equation, including state symbols, to show the formation of C.
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c) | Complete the table to show the expected observation upon addition of excess concentrated ammonia solution.
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Question 2
a) | State and explain the trend in boiling points down group 7 from fluorine to iodine.
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b) | State and explain the trend in electronegativity down group 7 from flourine to iodine.
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c) | Potassium halides react with concentrated sulfuric acid to form potassium hydrogensulfate and the different products shown in the table below. |
Explain, in terms of oxidation state changes, which halide is the strongest reducing agent in the reaction with concentrated sulfuric acid.
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Question 3
This question is about properties of the halogens and halide ions. Bromine can be extracted from sea water by bubbling chlorine gas through sea water. |
a) | Write the full electron configuration of a bromide ion.
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b) | Write an ionic equation for this reaction State why this reaction takes place in terms of halogen reactivity.
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c) | Precipitation reactions can be used to distinguish between halide ions. State the reagent needed for these precipitation reactions.
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d) | State the colour of the precipitates formed when silver nitrate is added to solutions containing the following halide ions. Chloride: precipitate Bromide: precipitate Iodide: precipitate white cream yellow
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Question 4
Describe and explain the relative reactivity of the halogens, chlorine, bromine and iodine, in their redox reactions with halides, using reactions on a test-tube scale. Include observations and relevant equations in your answer.
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Question 5
This question is about some redox reactions of chlorine, bromine and iodine. An excess of aqueous potassium bromide was added to chlorine water and the solution turned orange. |
a) | Write an equation, including state symbols, for this reaction.
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b) | Silver nitrate solution was added to the mixture in part a) and excess dilute ammonia solution was then added to the precipitate formed. Only some of the precipitate dissolved. Deduce why only some of the precipitate dissolved.
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c) | Aqueous potassium bromide was added to aqueous iodine, instead of chlorine water. There was no reaction. Give a reason why no reaction occurred.
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Question 6
This question is about some group 7 compounds. Solid sodium chloride reacts with concentrated sulfuric acid. |
a) | Give an equation for this reaction. Explain, in terms of oxidation states, whether this reaction is a redox reaction.
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b) | Fumes of sulfur dioxide are formed when sodium bromide reacts with concentrated sulfuric acid. For this reaction
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c) | Chlorine reacts with hot aqueous sodium hydroxide as shown in the equation: 3Cl2 + 6NaOH âž” NaClO3 + 5NaCl + 3H2O Give the oxidation state of chlorine in NaClO3 and in NaCl.
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d) | State the type of redox reaction shown in part c).
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Question 7
When concentrated sulfuric acid is added to solid potassium chloride, steamy fumes are produced. |
a) | Give the formula of the steamy fumes.
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b) | Write an equation for this reaction. State symbols are not required.
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c) | A redox reaction occurs when concentrated sulfuric acid is added to solid potassium bromide. A mixture of products is formed, including sulfur dioxide as the only reduction product. Give the oxidation number of sulfur in: i) sulfuric acid: ii) sulfur dioxide: 6 4
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d) | Complete the ionic equation for this redox reaction: H2SO4 + ....H+ + ....Br- âž” ........ + ........ + ....H2O
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e) | A redox reaction occurs when concentrated sulfuric acid is added to solid potassium iodide. Two reduction products are formed other than sulfur dioxide. Identify these two reduction products. In each case, give an observation that indicates the presence of the product.
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Question 8
Solid sodium halides react with concentrated sulfuric acid. A sample of solid sodium iodide is reacted with concentrated sulfuric acid. A black solid forms and hydrogen sulfide gas is produced. |
a) | Write a half-equation for the reaction of sulfuric acid to form hydrogen sulfide.
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b) | Write a half-equation for the formation of the black solid.
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c) | Use your answers to parts a) and b) to write an overall equation for the reaction of sodium iodide with concentrated sulfuric acid.
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d) | Give the role of iodide ions in their reaction with concentrated sulfuric acid. A acid B oxidising agent C reducing agent D catalyst
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e) | Write an equation for the reaction of solid sodium fluoride with concentrated sulfuric acid. State symbols are not required.
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f) | Suggest a reason why the reaction of sodium fluoride with concentrated sulfuric acid is different from the reaction with sodium iodide.
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Question 9
Sodium chlorate, NaClO3, contains the chlorate(V) ion. |
a) | Explain what is meant by the (V) in chlorate(V) .
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b) | Chlorine reacts with hot aqueous sodium hydroxide to form sodium chlorate. Write a balanced symbol equation for this reaction. State symbols are not required.
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c) | Explain, in terms of oxidation states, why this is a disproportionation reaction.
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Question 10
Chlorine is used in water treatment. |
a) | Write an equation for the reaction of chlorine with water.
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b) | Complete the dot and cross diagram for chloric(I) acid (HOCl). Use a triangle to represent the hydrogen electron, circles to represent the oxygen electrons and crosses to represent the chlorine electrons. Show the outer shell electrons only.
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c) | Predict the bond angle in chloric(I) acid. Explain your answer in terms of electron pairs.
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